1. Field of the Invention
The present invention relates to a method and a device for unpacking a stack of products packaged in a sleeve, such as a stack of covers for cans, for instance drinks cans.
2. Description of the Related Art
In the production of drinks cans the body of the can is usually punched, while after filling with the contents the cover is arranged in the filling opening for filling of the drinks can and is fixed there. For this purpose the covers are supplied in stacks which are packed per stack in a sleeve, for instance of paper. It is noted that the present invention is not limited to stacks of covers for drinks cans, but is applicable in the unpacking of all types of products packed in a sleeve which are stacked in the sleeve.
It is generally known to manually remove the sleeve from the stack of products. For this purpose a longitudinal cut, either linear or helical, is made in the packaging-like sleeve. The stack is then removed from the packaging and placed on a conveyor belt for further processing. This manual work is time-consuming and cannot usually be performed rapidly enough to keep up with the devices which process the products. In addition, the work is stultifying and can easily lead to mistakes, wherein the stack of products is set down the wrong way round and then presented the wrong way round to the device for further processing of the products, which can hereby jam.
Automated solutions are known, which are however all based on cutting through the sleeve in axial directionxe2x80x94linearly or helicallyxe2x80x94wherein the sleeves with the stacks of products therein must often still be placed manually in the automated unpacking device, which can still result in problems with the orientation of the products in respect of the devices for further processing.
EP-A-0,947,428 relates to a technique of longitudinally cutting the sleeve before discharge of the stacks of products, where the stacks and the associated sleeve are generally relatively long, for which purpose machines have to be used which must have a freedom of movement over correspondingly long distances. Such packaging devices hereby become complex and costly. Damage to the sides of the products can moreover occur with the longitudinal cutting movement in both manual unpacking processes and automated unpacking processes. This is a particular drawback in the case of for instance drinks cans, since it is then not possible to ensure that the finally assembled drinks cans are also made watertight. Damage resulting from the cutting of the sleeve is of course also undesirable in the case of other stacks of products packed in sleeves, precisely because the sleeve itself already serves to protect the stacks of products.
It is acknowledged that from U.S. Pat. No. 4,852,253 a technique is known for automatically unpacking relatively short stacks of coins wrapped in a wrapper.
The present invention has for its object to obviate the drawbacks of the above described known art, for which purpose a method and a device are provided, which are distinguished respectively by removing and means for removing a part of the sleeve located on a longitudinal end, peeling away the sleeve over the stack with an opposed relative movement of the stack and the sleeve and means for this purpose, and separately discharging the stack and means for this purpose.
Since only the part of the sleeve located at the longitudinal end is removed, the danger of damaging a whole stack of products is obviated. The unpacking process is considerably simplified and automation thereof made appreciably easier in accordance herewith, without exceptionally complex and costly equipment having to be employed for this purpose.
In a preferred embodiment the sleeve is tensioned over the stack on the longitudinal end and a cut is then made in the sleeve at that location. This ensures that the whole or partial removal of the portion of the sleeve located on the longitudinal end takes place accurately, particularly when the sleeve is arranged slightly loosely round the stack of products, as is the case with a paper sleeve. Tensioning of the sleeve can comprise of fixing the sleeve and pushing the stack of products in the fixed sleeve up against the longitudinal end of the sleeve. Use can be made for this purpose of for instance a hydraulic or pneumatic cylinder which presses against the end of the sleeve situated opposite the longitudinal end while the sleeve itself is fixed. This is particularly simple to realize.
The portion of the sleeve located on the longitudinal end can further be wholly or partly removed by perforating the sleeve wholly or partly around the longitudinal end thereof and further relying on pressing of the stack of products out of the sleeve during the relative movement of the stack and the sleeve. This can take place by arranging notches in the sleeve, which is extremely simple to realize, particularly when the sleeve is for instance manufactured from paper. When the products have a form corresponding with the pattern of notches, a safety can be provided which checks alignment of the notch and the recesses before the notches are arranged, and arranging of the notches takes place only when the alignment is correct. A safety is thus provided to prevent the possibility of the stack of products in the sleeve being unpacked the wrong way round and passed on to further processing equipment, with the purpose of preventing disruptions therein. The sleeve can further be fixed and the stack pressed through the radial pattern of notches by pushing up the stack in order to remove the portion on the longitudinal end of the sleeve. The number of cutting operations can hereby be minimized and limited to a minimal depth, whereby further damage to the products can be prevented with certainty. In the interim period between pushing up against the longitudinal end of the sleeve and pushing up through the longitudinal end the sleeve can be released for movement and be displaced in the direction of the end of the sleeve situated opposite the longitudinal end. The movement distance of all moving parts involved in fixing of the sleeve and pushing the stack up to and through the longitudinal end of the sleeve is hereby minimized, for which purpose machines with a small stroke can be used which are simple and relatively inexpensive.
Another embodiment will further be discussed hereinbelow for peeling away the sleeve over the stack of products. A part of the sleeve extending beyond the stack of products is herein engaged with a set of rotatable wheels which can be moved away from and toward each other. When the wheels engage the protruding part of the sleeve, they are driven in rotation in an opposing direction. The sleeve is hereby peeled from the roll of products. The wheels are of course then arranged on the opposite end of the sleeve opposite the removed longitudinal end such that the sleeve is peeled away from the stack by retraction between the wheels. In order to prevent the sleeve being crumpled, the wheels can be intermittently moved respectively away from and toward each other during driving thereof. This ensures that a movement of the sleeve being peeled away is always guaranteed in axial direction of the stack.